Connection element for the captive mounting of a lever-like cam follower

ABSTRACT

A connection element ( 9, 10 ) is provided for the captive mounting of a lever-type cam follower ( 1 ), which is used to actuate a gas-exchange valve ( 5 ) of an internal combustion engine, on a support element ( 2 ). The support element ( 2 ) has a spherical end ( 7 ) on which the cam follower ( 1 ) is pivotably mounted by a concave molding ( 6 ). The connection element ( 9, 10 ) is made from a flat material and is arranged, with a central section ( 11 ), on a bottom side ( 12 ) of a base ( 13 ) facing the support element ( 2 ). The base surrounds the concave molding ( 6 ) and connects to the side walls ( 27 ) of the cam follower ( 1 ). The central section forms, with two limbs ( 14 ) that are spaced apart from each other and a web ( 15 ) connected with the limbs, a U-shaped recess ( 16 ), which extends in a longitudinal direction of the cam follower ( 1 ) and which surrounds, in an essentially play-free manner, an annular groove ( 8 ) below the spherical end ( 7 ) in a fork-like manner and orthogonal to a pivoting direction of the cam follower ( 1 ). The limbs (14) transition into retaining grips ( 17 ) offset by approximately 90° and the web ( 15 ) transitions into a support wall ( 18 ) offset by approximately 90°. Retaining lugs ( 19, 20 ) located on the retaining grips and the support wall are engaged on a top side ( 21 ) of the base ( 13 ) facing away from the support element ( 2 ) for holding the connection element ( 9, 10 ) on the cam follower ( 1 ). The retaining grips ( 17 ) are supported on inner sides ( 26 ) of the side walls ( 27 ) of the cam follower ( 1 ) such that the U-shaped recess ( 16 ) is essentially fixed in position in a perpendicular direction relative to the cam follower ( 1 ) and in terms of a shape thereof.

BACKGROUND

The invention relates to a connection element for the captive mountingof a lever-type cam follower, which is used to actuate a gas-exchangevalve of an internal combustion engine, onto a support element with aspherical end. The cam follower is pivotably mounted on the sphericalend via a concave molding. Here, the connection element made from flatmaterial is arranged, with a central section, on a lower side of a base,which is oriented towards the support element. This base surrounds theconcave molding and connects to side walls of the cam follower. Theconnection element forms, with two limbs spaced apart at a distance fromeach other and also a web connecting these limbs, a U-shaped recess,which extends in a longitudinal direction of the cam follower and whichsurrounds a ring-shaped groove below the spherical end in a fork-likemanner.

In a known way, such connection elements allow the generation of acomponent, which includes, for example, a finger lever as a cam followerand a support element. Such a component then minimizes the risk ofpotentially incorrect assembly by the customer. Among other things, thiscould consist in the finger lever being mounted rotated by 180° in thevalve train. In this case, the contact partners of the spherical head ofthe support element and the spherical cap of the finger lever and alsothe valve shaft end and the corresponding counter surface on the fingerlever being interchanged. Such an incorrect assembly would lead at leastto incorrect functioning of the valve train and even, in the worst case,to serious engine damage. Additional requirements on this connectionelement consist in that, on one side, a separation of the finger leverand support element due to transport effects is reliably ruled out and,on the other side, the connection element does not contributedisadvantageously to valve-drive wear in the pivoting motion of thefinger lever on the support element.

In DE 196 17 523 C2, different variants of a connection elementsatisfying the requirements noted above are proposed. This connectionelement engages in the ring-shaped groove below the spherical end forcaptive connection of the finger lever and support element. The materialthickness of the connection element is matched to a width of the groove,so that it can move freely in the groove into every pivoting position ofthe finger lever. Thus, the finger lever can execute a pivoting motionin the actuation direction of the gas-exchange valve, which is notimpaired by frictional effects of the connection element. In one ofthese variants according to the FIGS. 3 and 4 of the mentionedpublication, the connection element is made of flat material andsurrounds the finger lever at the concave molding in a U-shapedconfiguration with two limbs oriented in the direction of thegas-exchange valve. At their end, these limbs transition into retaininglugs, which snap behind the material surrounding the concave molding forfixing the connection element in the longitudinal direction of thefinger lever. Furthermore, in this variant, the limbs form a U-shapedrecess and surround the annular groove in a fork-like manner. TheU-shaped recess is here embodied open towards the gas-exchange valve.

In general, in the assembly of the finger lever with the supportelement, it is typical to clip the spherical end of the support elementbehind a recess of the connection element engaging in the groove. Inthis way, the connection element is already mounted on the finger lever.Such an assembly process is now also possible and is to be performedonly using these means for the previously mentioned variants of thecited publication. This is based on the condition that pushing theconnection element in the longitudinal direction onto the finger leveris not possible for a spherical end of the support element held in theconcave molding, because the retaining lugs necessary for attachmentspread out the lower limb of the connection element before reaching theend position and would collide with the piston periphery of the supportelement below the annular groove.

A prerequisite for trouble-free clipping of the support element behindthe recess of the connection element is now its elastic deformation inthe area of the recess. The necessary elasticity can be achieved withouta problem through the suitable geometry of the recess and also suitableproperties and thickness of the connection element material.Nevertheless, a mounting gap remains perpendicular to the actuationdirection of the finger lever between the connection element and theannular groove in the support element. Consequently, the finger lever isalso not completely hindered by the connection element for a pivotingmotion perpendicular to its actuation direction, wherein this pivotingmotion can then equal up to 15°. Such tipping of the finger lever aboutits longitudinal axis can also occur when it is mounted in the internalcombustion engine, namely if there is a loss of contact between thefinger lever and the actuating cam. Causes for such a loss of contactcan be an undesired lowering of the usual support element with hydrauliclash compensation or jumping of the finger lever from the actuated camas a result of overspeed in the internal combustion engine.

In this respect, in particular, finger levers with very narrow camcontact surfaces are to be considered. These can be used in installationspace-limited multi-valve engines or also in variable valve controllers,in which a cam arrangement comprising several cams of different strokeis mounted so that it can be displaced axially on its camshaft and isbrought into engagement with the finger lever by the one cam matchingthe operating state of the internal combustion engine. The finger leveris then especially at risk in terms of further or complete tipping ofthe support element, because it may no longer be sufficiently alignedwith the cam due to the narrow cam contact surface when contact to itscam is restored.

SUMMARY

Therefore, the object of the invention is to provide a connectionelement of the type named above, in which the cited disadvantages areovercome, so that a stable alignment on the actuating cam can beguaranteed in all operating states of the internal combustion engineespecially for cam followers with narrow cam contact surfaces.

The solution of this objective emerges from the features of claim 1,while advantageous refinements and constructions are to be taken fromthe dependent claims.

Consequently, the objective is met in that the U-shaped constructionsurrounds the groove orthogonal to the pivoting direction of the camfollower essentially without play, wherein the limbs transition intoretaining grips offset by approximately 90° and the web transitions intoa support wall offset by approximately 90°. This support wall hasretaining lugs that latch onto a top side of the base facing away fromthe support element for holding the connection element on the camfollower. The retaining grips are supported on the inner sides of theside walls of the cam follower such that the U-shaped recess isessentially fixed in terms of its position in the perpendiculardirection to the cam follower and in terms of its shape.

Here, the previously noted disadvantages are overcome with simple means.The construction of the connection element guarantees that the camfollower forms a captive connection to the support element andsimultaneously its ability to tip about its longitudinal direction isminimized. The latter is mainly achieved in that the U-shaped recesssurrounds the groove orthogonal to the pivoting direction of the camfollower without play. The prerequisite for this condition is that thesupport element can be mounted essentially simultaneously with theconnection element on the cam follower. This happens in an intermediateassembly step, such that the connection element is initially locatedonly on one side, i.e., either with the retaining grips or with thesupport wall behind the base, which surrounds the concave molding. Inthis assembly state, there is still sufficient spacing between theU-shaped recess of the connection element and the bottom side of thebase, so that now the support element can be pushed between the limbs ofthe U-shaped recess with its annular groove. In a last assembly step,the spherical end of the support element is then brought into contactwith the concave molding of the cam follower, while the retaining lugsof the retaining grips and the support wall are simultaneously clippedbehind the base.

Thus, elastic deformation of the connection element, as occurs for laterclipping of the support element, and also the associated assembly gapbetween the connection element and the annular groove are no longernecessary. The low elasticity requirement further allows the use of aconnection element of greater material thickness, which effectivelyprevents tipping of the cam follower, also through high componentstiffness, in addition to the freedom of play relative to the annulargroove. Nevertheless, the material thickness of the limbs can be limitedwithout a problem, so that the thickness is less than an axial width ofthe groove, so that the connection element is freely movable in thegroove geometrically for pivoting movements of the cam follower in theactuation direction of the gas-exchange valve. In this respect, theconnection element participates without deformation in the pivotingmovement of the cam follower and also generates no additional frictionwhen the gas-exchange valve is actuated.

The retaining grips preferably have an S-shaped, curved or equal actionconstruction on an end section that includes the retaining lug. Such ashape of the retaining grips causes an extended and more stable supportof the retaining grips in terms of torsion on the inner sides of theside walls of the cam follower. Moreover, in a first exemplaryembodiment of the connection element, the assembly of the component issimplified, because the connection element can be suspended behind thebase, which surrounds the concave molding, with play but with a captiveconnection during the assembly process.

According to a second preferred embodiment of the invention, theS-shaped or equal action end section of the retaining grips are providedwith lateral pegs, which engage in corresponding groove-shaped recesseson the inner sides of the side walls of the cam follower supporting theretaining grips. This positive-fit construction provides additionalsecurity against undesired detachment of the connection element from thecam follower. Here, for example, in the critical operating states namedabove for the internal combustion engine, there is a residual risk thatnever can be completely ruled out.

The connection element should further preferably be comprised of aspring-like material, such as cold-hammered steel, for mounting on thecam follower. Alternatively, light metal or plastic, which is reinforcedwith fibers or particles, could also be used.

The lever-like cam follower is preferably a finger lever. This fingerlever can have a sliding surface or especially preferred also arotatably mounted roller as a cam contact surface. Finally, the fingerlever should have a generally U-shaped cross section. Instead of theU-shaped cross section, only one U-type cross section or one H crosssection or the like can also be provided. In combination with thisfeature, the finger lever is made from sheet-metal material. At thispoint, other materials suitable for this function are naturally alsoconceivable, that is, also plastics or finger levers formed throughreshaping, wherein the U shape without a combination with thesheet-metal material is also included in the protective area of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail with reference to the attacheddrawings, in which embodiments are shown. Shown are:

FIG. 1 a perspective view of a first embodiment for the connectionelement according to the invention,

FIG. 2 a perspective view of a second embodiment for the connectionelement according to the invention,

FIG. 3 a perspective view of the connection element according to FIG. 2in the assembled state of the valve train for a cam follower shown inlateral cross-section, and

FIG. 4 a rear view of the valve train in partial section with theconnection element from FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 3 and 4 show a cam follower 1 and a support element 2, whichsupports the cam follower so that it can pivot and which is hereconstructed with hydraulic lash compensation that is not shown in moredetail. The cam follower 1 is driven in a known way via a cam 3 by aroller 4 connected to the cam follower 1 and mounted rotatably in theactuation direction of a gas-exchange valve 5. Obviously, instead of theroller 4, a sliding surface connected rigidly to the cam follower 1 canalso be provided as the cam contact. In the illustrated embodiment, thecam follower 1 is a finger lever, which has a U-shaped cross section andis preferably made from sheet-metal material in a reshaping process.

As is further visible from the mentioned figures, the cam follower 1 hasa concave molding 6, by which it is mounted on a spherical end 7 of thesupport element 2. Below the spherical end 7 there is an annular groove8, in which a connection element 9 or 10 engages, as illustrated in theembodiments according to FIG. 1 and FIG. 2, respectively, as individualcomponents. The connection element 9, 10 contacts a bottom side 12 of abase 13 facing the support element 2 with a central section 11. Thisbase surrounds the concave molding 6. The central section 11 has twolimbs 14, which are connected to each other by a web 15 and form aU-shaped recess 16 in the longitudinal direction of the cam follower 1.It is visible particularly from FIG. 4 that the limbs 14 surround thegroove 8 without play perpendicular to the actuation direction of thecam follower 1.

The limbs 14 transition into retaining grips 17 offset by approximately90° in a longitudinal direction of the cam follower 1. A support wall 18similarly offset by approximately 90° is connected to the web 15. Here,retaining lugs 19, 20, which are engaged on a top side 21 of the base 13that faces away from the support element 2 in the completely assembledstate of the component formed from the cam follower 1, support element2, and connection element 9, 10, are constructed on the retaining grips17 and on the support wall 18. Therefore, the connection element 9, 10is held on the cam follower 1 together with the support element 2 in thelongitudinal direction of the support element 2. The connection element9, 10 is fixed in the longitudinal direction of the cam follower 1 bythe retaining grips 17 and the support wall 18, which surround ends 24,25 of the base 13 with bottom sections 22, 23. Finally, the U-shapedrecess 16 is aligned in the perpendicular direction to the cam follower1, such that the retaining grips 17 are supported on the inner sides 26of the side walls 27 of the cam follower 1.

The retaining grips 17 each have a preferably S-shaped, curved or equalaction construction on an end section 28, which includes the retaininglug 19. This produces, on one hand, an extended support of the retaininggrips 17 that is more stable in terms of torsion on the inner sides 26of the side walls 27 of the cam follower 1.

On the other hand, the retaining grips 17 shaped in this way simplifythe assembly of the component including the connection element 9,because the connection element 9 can initially be suspended on one sidewith play but with a captive connection behind the base 13, whichsurrounds the concave molding 6. In this partly assembled state there isstill sufficient spacing between the U-shaped recess 16 of theconnection element 9 and the bottom side 12 of the base 13, so that nowthe support element 2 can be pushed between the limbs 14 with itsannular groove 8. In a last assembly step, the spherical end 7 of thesupport element 2 is brought into contact with the concave molding 6 ofthe cam follower 1, while the retaining lugs 19, 20 of the retaininggrips 17 and the support wall 18 are simultaneously clipped onto the topside 21 of the base 13.

As can be identified easily in FIG. 2, the S-shaped, curved or equalaction retaining grips 17 of the connection element 10 are also providedwith lateral pegs 29. These pegs 29 are snapped with a positive fit intogroove-shaped recesses 30 in the inner sides 26 of the side walls 27 ofthe cam follower 1. In this way, additional security is given againstundesired detachment of the connection element 10 from the cam follower1.

Because the annular groove 8 of the support element 2 is pushed betweenthe limbs 14 of the connection element 9, 10 mounted in advance on thecam follower 1, the connection element 9, 10 can be constructed with agreater material thickness with low elasticity, in order to effectivelyprevent tipping of the cam follower 1 also through high componentstiffness, in addition to the freedom from play relative to the groove8.

Nevertheless, the limbs 14 have a material thickness that is less thanthe axial width of the groove 8. Thus, the connection element 9, 10 canmove freely in the groove 8 in the actuation direction of thegas-exchange valve 5 for pivoting movements of the cam follower 1, sothat it neither deforms nor contributes to friction when the internalcombustion engine is running.

Naturally any materials can be used for the connection element 9, 10according to the invention as long as the technical and also financialdemands are satisfied. Thus, in addition to spring-like steel andlight-metal materials, plastics, which can have particle or fiberreinforcement, are also obviously possible. Due to their low density,these materials have a negligible contribution to the moving masses ofthe valve train.

REFERENCE SYMBOLS

-   1 Cam follower-   2 Support element-   3 Cam-   4 Roller-   5 Gas-exchange valve-   6 Concave molding-   7 Spherical end-   8 Groove-   9 Connection element-   10 Connection element-   11 Central section-   12 Bottom side-   13 Base-   14 Limb-   15 Web-   16 U-shaped recess-   17 Retaining grip-   18 Support wall-   19 Retaining lug-   20 Retaining lug-   21 Top side-   22 Bottom section-   23 Bottom section-   24 End-   25 End-   26 Inner side-   27 Side wall-   28 End section-   29 Peg

1. Connection element for the captive mounting of a lever-type camfollower, which is used to actuate a gas-exchange valve of an internalcombustion engine, on a support element, which has a spherical end, onwhich the cam follower is pivotably mounted by a concave moldingthereof, the connection element comprising a flat material has a centralsection, on a bottom side of a base of the cam follower facing thesupport element, the base surrounds the concave molding and connects toside walls of the cam follower, and the connection element forms, withtwo limbs that are spaced apart from each other and a web connected withthe limbs, a U-shaped recess, which is arranged in a longitudinaldirection of the cam follower and which surrounds an annular groovebelow the spherical end in a fork-like manner, characterized in that theU-shaped recess surrounds the groove orthogonal to a pivoting directionof the cam follower essentially without play, the limbs transition intoretaining grips offset by approximately 90° and the web transitions intoa support wall offset by approximately 90°, with retaining lugs locatedon the retaining grips and the support wall, which are engageable on atop side of the base facing away from the support element for holdingthe connection element on the cam follower, the retaining grips aresupported on inner sides of the side walls of the cam follower such thatthe U-shaped recess is essentially fixed in position in a perpendiculardirection relative to the cam follower and in terms of a shape thereof.2. Connection element according to claim 1, wherein at least one of theretaining grips has a generally S-shaped end section, which includes theretaining lug.
 3. Connection element according to claim 2, wherein theend section has a lateral peg, which is engageable in a groove-shapedrecess in the inner side of the side wall to support the retaining grip.